1. Field of the Invention
The invention relates to a device for controlling the temperature and pressure of fluid within a container used to thermally treat body tissue. More particularly, the present invention relates to an expandable device filled with fluid, with a heating assembly and pressure control valve within the expandable device.
2. Description of Related Art
Application of thermal energy has been used for some time to treat body tissues. One method of controlled application of thermal energy involves the use of a balloon or similar container filled with fluid at an elevated temperature and pressure. The balloon is placed against the tissue to be treated, and the heat from the fluid is conducted through the walls of the balloon and into the tissue.
Application of thermal energy with fluid-filled balloons has been of particular use in treating tissue in body cavities of animals, including humans. For example, balloons filled with heated fluid have been used to effect coagulation and/or cauterization of a uterine endometrium.
A method is known for effecting necrosis of the endometrium by inserting a distensible bladder into the uterus. The distensible bladder is inflated to a predetermined pressure with a fluid so that the distensible bladder is in contact with substantially all of the tissue lining for which necrosis is desired. The fluid is heated to a temperature sufficient to coagulate and/or ablate the tissue lining. The temperature and pressure of the fluid is controlled by means connected to the distensible bladder. The bladder is maintained inflated with the fluid at a temperature for a period of time sufficient to effect necrosis of the endometrium.
Early methods for heated-balloon therapy required the fluid to be preheated outside the body, and then pumped through conduits into the balloon or other bladder. Another method for heated-balloon therapy involves positioning a heating element coil in the balloon, and causing an electrical current to pass through the coil, thereby heating the coil and the surrounding fluid. Such heating systems require accurate temperature monitoring and control. Various temperature monitoring and control systems are known in the art, but many temperature control systems are relatively expensive and of varying reliability.
Controlling the pressure within the balloon is another concern, particularly in gynecological and other endoscopic procedures. Pressure control is of particular concern to prevent overinflation, and possibly bursting, of the balloon. External pressure monitors are known in the art, but can be relatively expensive.
Consequently, there is a need to improve heated, pressurized fluid systems to provide effective control of the fluid temperature and pressure while at the same time allowing for reduced system cost. The present invention satisfies these needs.